1. Field of the Invention
The present invention relates to a support member or support frame, particularly wire frame, web frame or section frame, for preferably continuous conveying installations for flat, thin and bendable objects, such as plates or sheet metal, which have been provided with a fresh surface coating. The continuous conveying installation is provided, for example, in a drying tunnel or a tunnel for thermal treatment or a storage unit for the objects between two successive processes or the like.
2. Description of the Related Art
2.
Wire frames of the above-described type are usually mounted in parallel arrangement one behind the other on one or more chains or similar devices. The plates or sheet metal pieces are continuously transported by means of the wire frames, so that the plates or sheet metal pieces can be conveyed through a tunnel for drying or thermal treatment or can be held in a waiting position between two successive work processes in the same production line.
Conveyor installations of this type are well known and are frequently used. FIG. 1 of the drawing schematically shows a typical example used in the metal packing industry. The metal packing industry requires thin iron sheets or aluminum plates which are varnished, imprinted or coated for protection or for optical reasons. For this purpose, it is necessary that the sheet plates dry or polymerize at temperatures of between 120.degree. C. and 220.degree. C. for approximately ten minutes in a tunnel b, so that the paint or the like securely adheres to the metal and can protect or ornament the plate. The purpose described above is only an example because the wire frames can also be used for supporting all types of flat and thin articles which are transported in an almost vertical position, wherein the time of treatment of the plates is determined by the length of the tunnel.
FIG. 1 of the drawing shows a plate or sheet metal coating unit a and a belt conveyor arrangement b for inserting the plates between the wire frames 1 of a continuous conveyor installation c. FIG. 1 also shows an unloading unit with belt conveyor arrangement d toward a stacking unit e.
FIG. 2 of the drawing shows in a top view a typical wire frame 1 with support extensions 7 for a conveyor installation for conveying metal plates through a drying tunnel. Additional support extensions, shown in broken lines, are provided if especially large metal plates are to conveyed.
FIG. 3 shows the same wire frame in section. FIG. 2 shows a sheet metal plate of maximum length and maximum width in broken lines.
The wire frame 1 is constructed in accordance with a compromise between two contradictory necessities. First, a large and robust support surface must be available which is suitable for a large number of different plate or sheet metal sizes, and a minimum mass must be provided, so that the energy requirement for repeatedly heating to processing temperature per hour is reduced. The wire frames usually are of welded or riveted flat section steel, as shown in FIG. 2. On the other hand, it has been customary until today to insert the two surfaces between two parallel planes, so that they can be aligned without problems on a rolling plate if they have buckled or been deformed as a result of a problem during transport (FIG. 3).
The wire frames are installed on one or more chains 2, as shown in FIG. 4. The wire frames are mounted on the chain or chains such that the angle between the vertical and the plane of placement of the wire frames is approximately 15.degree., so that the plates being transported rest on the wire frames in a defined manner on that surface which is opposite the side which has just been imprinted or coated, i.e., on the back side, so that the front side does not come into contact with the preceding wire frame. In conveyor systems of sound construction, U-shaped parts 3 fastened at the top to the wire frames serve as transverse connections between two successive wire frames. The resulting cage-like arrangement ensures that the wire frames which are moved in a row are practically non-deformable.
Wire frames of the above-described construction have in the past been entirely satisfactory as long as the lengths and heights (dimensions of the almost vertical plate during transport) had a relationship relative to the thickness which ensured that the plates did not bend under their own weight and remained resting against the wire frames essentially plane, as can be seen in FIG. 4, reference numeral 4.
In order to utilize metal more effectively, there is the tendency to increase the size of each plate and to reduce the thickness thereof. In conventional conveyor installations, large and thin plates are easily bent, as indicated in FIG. 4 by reference numeral 5, so that undesirable contacts between the plates and the rear sides of the preceding wire frames occurred more frequently. The contact results in insufficient protection and/or undesirable spots which make the plates essentially useless. The described tendency can also be found in plates of light metal which is less stiff than steel.